New simple route of synthesis combining soft and hard templates to prepare high specific area mesoporous carbon electrodes for Li-air batteries

GONZALO MONTIEL; EDUARDO FUENTES; MATÍAS FACTOROVICH; MARIANO BRUNO; FEDERICO VIVA; HORACIO CORTI

San Salvador de Jujuy

Workshop; IWLiME 2016: 3rd International Workshop on Lithium, Industrial Minerals and Energy; 2016

Univerisdad Nacional de Jujuy

Is well known that Li-air batteries (LAB) are called to be the next generation of lithium batteries because of its super-high specific energy density of 11,140 Wh.kg-1 rivaling that of gasoline[1]. Electrodes materials stability is one of the actual challenges of LAB development. Cathode electrode, commonly named as air electrode, is undoubtedly considered as the most important part of the LAB[1]. Modeling studies of pore size at air cathode has demonstrated that pores smaller than a critical size does not contribute to the discharge of the battery. The discharge capacity gradually increases when the mean pore size of the electrode ranges between 10 and 50 nm, while capacity decreases when the mean pore size increases to 100 nm[2]. With the motivation of preparing optimal air carbon electrodes, a new simple route of synthesis combining soft template (ST) and hard template (HT) was applied to obtain tailored mesoporous carbons (MC) from carbonization of resorcinol formaldehyde (RF) [3,4]. The hollow HT silica spheres (Aerosil or Sipernat) are surrounded and filled by the resin. After carbonization at 1000ºC for two hours, and removal of the HT with concentrated NaOH aqueous solution, the porous carbon is obtained.By adjusitng the HT/ST proportion different MCs are obtained. Pore distribution and surface area was determined on the various carbons obtained. BET specific surface area of the MC synthesized with Aerosil varied between 494 m2g-1 and 665 m2g-1 and total pore volume from 0.89 cm3g-1 to 1.40 cm3g-1. Meanwhile BET specific surface area of MC synthesized with Sipernat varied between 662 m2g-1 and 998 m2g-1 and its pore volume from 0.75 cm3g-1 to 1.70 cm3g-1. Pores width distributions, are mainly focused in two regions 5-10 nm and 20-60 nm, these are called to the most suitable ranges of pores to increase discharge capacitance of air cathodesMCs were combined with different binders and electrodes were assembled to evaluate their electrochemical behavior in aqueous electrolyte, 3 M H2SO4. Specific capacitance was calculated by using integration of the voltammogram, galvanostatic charge/discharge and electrochemical impedance spectroscopy.  Monolithic MCs, prepared using Sipernat as HT, were studied in relation to the partition and diffusivity of lithium salts in the pores. Cell assemblies with Swagelok® hardware will be prepare to test carbon air cathode with non-aqueous and hybrid electrolytes.